Well, we had one of these back on the old forum, and I'm surprised this hasn't come up yet here, so I'll start it.
This is my new Visual Novel obsession, and it's even more kick ass now that the updated release is voiced.
I'll give a short summary of Fortissimo//Akkord:Bsusvier since I want to share my reasons for loving it. I was first intrigued by the good CG's, and it also applies to my love of things the emulate Fate/Stay Night. Most are pretty fail, but so far Fortissimo has me as captivated (if not more) than Fate did.
As I said, this emulates Fate/Stay Night, in that on the island this story takes place, 13 people who are gifted with magic (whether they are aware of it or not) are gathered and a battle royal is thrust upon them, called Ragnarok, with the winner received any wish they want. This already brings reference to the Holy Grail War and 7 Masters and Servants, but also takes another page in that many of the weapons and abilities each of the participants have are lifted from Norse legend, as many might have guessed since the War is Ragnarok.
Truthfully, I cannot say exactly which weapons, etc. are emulated here, since I don't know the legend well enough, and my translation program kinda breaks when they try to say something in English.
Also, another page, everyone can be viewed with their stats and parameters, and their different techniques via a separate screen that brings to mind the Status screen from Fate.
While it is a Fate clone, Fortissimo is the only similar VN other than Princess Waltz that I've played for longer than an hour, and I'm freaking LOVING IT.
-Edit, slight NSFW at the end, kinda missed it.